I will try to make a simple and straight forward guide to completely new players in the game.
If this guide helped you, please post a reply about it. I would love reading it.

Introduction
When you start the game for the first time you will be a Knight with Sword and Shield.
Knight is the tank class in this game. The job of a knight is to be the one taking the most damage from mobs and bosses so the Archer class can focus on crowd control and dealing damage.
Knight does melee damage with the sword.
You can become an Archer later when you have made 50k gold from collecting gold and selling items from maps.

Gems and Gold
There are two kinds of currency in the game. Gems and Gold.
You can see how much Gems and Gold you got by looking at the top right corner.
Gems can be used for a variety of different things in the game, but I will recommend that it is only used to add inventory space/storage space/skill points.
Gems can be acquired by playing the maps several times or bought with real money.
Be careful with your Gems. Don’t just waste them on anything. When you have gotten all the Gems you can get from the maps you will have to pay real money to get more. Therefore you should only use them on things that will be with you forever like inventory space/storage space/skill points
Gold can be used to identify items, buying food, ale, unlock the Archer class, upgrade Forge level and Cooking level.
Gold can be acquired from drops on maps or by selling items or bought with real money.

Food and Ale
There is two kinds of regeneration potions in the game. Food and Ale.
Food gives your health. You can see how much health you have by hovering the mouse over the red bar in the bottom.
Ale gives you valor. You can see how much valor you have by hovering the mouse over the blue bar in the bottom.
You can buy food and ale at the NPC called Bertha or craft better food and ale at the NPC called Lorian.
Some of the ingredients used to craft better food and ale can be bought from the NPC called Bertha and other ingredients can be found as drops on maps.
In the beginning of the game the cheapest food and ale is fine, but as you progresses you should switch to better food and ale to match the increase in your health and valor.

Gear
You can see your gear by clicking on the “Items” button in the bottom right corner or by clicking “I” on your keyboard.
In the beginning you should just focus on getting all the different parts of gear and equip it on your Knight.
As you progresses you will quickly find out that green/purple/orange gear requires to be identified before you can wear it. You can identify gear at the NPC called Byron.
Green is the least rare and therefore cost the least to identify, where orange is the rarest and therefore cost the most to identify.
To make more gold you should focus on gear that increases gold.
To get more gear from drops you should focus on gear that gives item find.

Skills
You can get to your skills by talking to the NPC called Caleb.
There are two different kinds of skills: Active Skill and Passive Aura.
Active Skill require valor to use and are something temporary like for example special attacks, temporary buffs or decoys.
When you have leveled up an Active Skill it will show up at the bottom with an number below it. You can use the Active Skill by clicking on it with the mouse or by pressing the number it has on the keyboard.
Passive Aura don’t require valor to use and gives a buff for every player in the party.
It is very individual what skills players use but here is what I recommend.
First get Maim to level 1 and then never level it higher than that.
Don’t ever level up Cleave, Charge, Hurl and Regeneration. The other skills are much better than those.
When you become level 15 you should put 1 skill point on Rumble. It stuns most types of mobs for a few seconds.
When you become level 25 you should reset your skills and put 10 skill points on Whirl. It is a very effective attack for attacking multiple mobs at the same time.
To learn more about the different skills effects on different levels, check this post: KingsRoad Skill Rank Effects List

Maps
You can get to the map selection at the NPC called Emil.
There are two different difficulties for all maps. Normal and Heroic.
You should stick to Normal difficulty in the beginning. When you have finished the map on Normal difficulty you can try the map on Heroic difficulty for more gold and drops.
The first couple of maps can easily be soloed on Normal difficulty, but as you progresses it will get harder. When a map becomes to hard you should try using the “Find Party” button and play the map together with other players.

Xp Farming Guide by Draxx

I have played the last 3 maps and written down how much XP and amount of XP potions i got.
I played the maps solo on normal and killed all mobs and obstacles.
The only item I have equipped that makes an impact on XP is a ring that gives +3 XP per kill.